With the development of network communication technologies, current networks can carry various types of services, such as audio, video, network game, and net browsing. In recent years, network bandwidth demands have increased at an exponential rate. Though the operators have increased the capabilities of networks carriage and data transmission by continuously increasing physical bandwidth and developing relevant technologies, the increase in physical bandwidth always lag behind the demands of users for data transmission. Confronting the problem about huge amount of data, people have conducted many researches on how to ensure the reliability of transmission and Quality of Service (QoS) of multiple services when the network carries the multiple services. In the latest two years, operators generally select Gigabit-Passive Optical Network (GPON) as the solution for future big bandwidth optical fiber access (Fiber to The Building/Cabinet/Curb/Home, and FTTx for short). This poses a higher requirement for the bandwidths of the metropolitan area networks. In addition, it requires that the metropolitan area networks have the capabilities of interfacing with GPON, which supports the development of future FTTxs.
Current metropolitan area networks can be classified into many types, such as Next Generation Synchronous Digital Hierarchy (NG-SDH), Metro Wavelength Division Multiplexing (Metro-WDM), and Layer 2 Ethernet. Current metropolitan area networks have at least the following problems: coexistence of multiple ways of transmission, excessive types of carriage technologies, poor transparency of services, lack of dynamic control protocols, difficult management and maintenance, lack of real time dynamic bandwidth adjustment mechanism, low utilization of network bandwidth, no strict QoS guarantee, and difficulty of satisfying big Bandwidth on Demand (BOD) services. To sum up, a relatively simple technology is urgently required in the prior art. In such a technology, it is capable of carriage multiple future services, convenient to interface with GPON, easy to carry out uniform adaptation of multiple services with dynamically allocated bandwidths, and capable of achieving channel carriage according to QoS characteristics.